1. Field of the Invention
The present invention generally relates to the field of optoelectronic communications, and more specifically to an optoelectronic hybrid package assembly including an integral fiber optic connector.
2. Description of the Related Art
Optoelectronic communication systems utilizing optical fibers as transmission lines include various transmitting and receiving modules. These modules conventionally include a hybrid microcircuit component having a light emitting diode (LED) or laser diode (for a transmitter); or a photodiode or other photodetector (for a receiver); integrated with signal processing circuitry on an integrated circuit chip or die. The component is mounted in a package housing or enclosure which is hermetically sealed for protection of the microcircuit. The module must further necessarily include a means for optically connecting the internally mounted microcircuit component to an optical fiber network external of the package.
A first prior art method of making such an external connection is illustrated in FIG. 1. An optoelectronic assembly 10 includes a rectangular housing or enclosure 12 in which an optoelectronic hybrid microcircuit component 14 is hermetically mounted. The component 14 includes a light propagating portion 14a, which may be a transmitter (LED or laser diode), or a receiver (photodetector). The light propagating portion 14a generally has a relatively small effective area, typically on the order of 50 microns wide.
The component 14 is optically connected to an external communication network by means of an optical fiber 16 in a "flying lead" configuration. The optical fiber 16 includes a transparent, light transmitting core 16a formed of glass plastic, or other suitable material. The core 16a typically has a central portion with a relatively high index of refraction, and a cladding layer with a lower index of refraction coaxially formed over the central portion. A buffer or jacket 16b made of a polymer or electrically conductive metal is coaxially formed over the cladding.
An end of the optical fiber 16 is inserted into the housing 12 through an opening 12a formed through a side wall 12b thereof. Further illustrated is a strain relief sleeve 18 which extends outwardly from the wall 12b to prevent flexure of the optical fiber 16 inside the housing 12, and increase the bend radius of the fiber 16 where it exits the housing 12.
Further illustrated in FIG. 1 is a connector 20 attached to the end of the optical fiber 16 external of the housing 12. The assembly 10 is often manufactured and shipped to an end user without a connector 20 attached, due to the numerous types of optical communication networks existing in the field which utilize many variant types of connectors, and the impracticality of stocking a particular assembly 10 with many different types of connectors. The optical fiber 16 which extends from the housing 12 as a flying lead is on the order of 125 microns in diameter, extremely fragile, and can be easily broken during shipping, installation, or maintenance, requiring time consuming and expensive reworking. In addition, attachment of the optical fiber 16 to the connector 20 is a high risk operation which is both time consuming and low in yield, resulting in a costly package configuration.
As illustrated in FIG. 1, a support member or block 22 is disposed in the housing 12 for retention and alignment of the optical fiber 16 therein. During fabrication of the assembly 10, the end of the optical fiber 16 is inserted into the housing 12 through the opening 12a as shown. However, due to the very small effective area of the light propagating portion 14a of the component 14, the end of the optical fiber 16 must be precisely aligned to the portion 14a. This is done by connecting the external end of the fiber 16 to an optical transmitter or receiver (depending on the type of light propagating portion 14a), connecting the component 14 to an electronic test instrument (not shown), moving the internal end of the fiber 16 until maximum optical coupling is detected by the test instrument, and then fixing the optical fiber 16 to the support block 22 by a chemical adhesive such as epoxy, soldering, or other applicable method as indicated at 24. This alignment process is time consuming, resulting in low yield and high expense, and subjects the optical fiber 16 to processing steps in which it is exposed to high risk of breakage.
The flying lead configuration of FIG. 1 is also highly inefficient in the utilization of space. Another prior art arrangement which eliminates the flying lead and is more space efficient than the assembly 10 is shown in FIG. 2. An optoelectronic assembly 30 includes a housing 32 in which is mounted a component 34 having a light propagating portion 34a. A transparent window 32a made of quartz glass or the like is fitted in an opening formed through a wall 32b of the housing 32. The component 34 is mounted such that the light propagating portion 34a is disposed as close as possible to the window 32a.
The configuration of FIG. 2 does not include an optical fiber, and thereby eliminates the problems associated therewith. However, only one mounting position for the component 34 in the housing 32 is possible, which further permits the mounting flexibility of another component 36 such as a Peltier cooler. Although the internal alignment problem regarding the light propagating portion 34a has been eliminated, the problem of aligning the light propagating portion 34a to an external optical fiber (not shown) for optical interconnection with other network elements remains. Typically, a bayonet or threaded connector 32c is used for this purpose. However, mechanical alignment of the optical axis of the connector 32c to the light propagating portion 34a of the component 34 requires precise and expensive process steps.